Use of a particular copolymer for preventing deposits on the valves of indirect injection petrol engines

ABSTRACT

The copolymers according to the invention are very particularly effective in preventing and/or cleaning the deposits on the valves while preventing the latter from sticking at low temperature.

A subject matter of the present invention is the use of a specificcopolymer to prevent the deposits which form at low temperature on thefuel intake valves in indirect injection spark ignition engines.

PRIOR ART

Liquid fuels for internal combustion engines contain components whichcan decompose during the operation of the engine. The problem ofdeposits in combustion engines is well known to auto mechanics. It hasbeen shown that the formation of these deposits has consequences on theperformance qualities of the engine and in particular has a negativeimpact on consumption and emissions of particles. Progress in thetechnology of fuel additives has made it possible to confront thisproblem. “Detergent” additives used in fuels have already been proposedto keep the engine clean by limiting deposits (“keep-clean” effect) orby reducing the deposits already present (“clean-up” effect). Mentionmay be made, by way of example, of U.S. Pat. No. 4,171,959, whichdescribes a detergent additive for gasoline fuel containing a quaternaryammonium functional group. WO 2006/135881 describes a detergent additivecontaining a quaternary ammonium salt used for reducing or cleaningdeposits, in particular on the intake valves.

In the case of indirect injection spark ignition engines (or gasolineengines), a specific problem is posed, related to the formation ofdeposits on the external parts of the engine and in particular on thestems of the intake valves for the mixture of air and fuel upstream ofthe combustion chamber, which results in a phenomenon of valve sticking.

This phenomenon, well known to specialists under the term “valvesticking”, is described in a reference publication by Seppo Mikkonen,Reino Karlsson and Jouni Kivi entitled “Intake Valve Sticking in SomeCarburetor Engines”, SAE Technical Paper Series No. 881643,International Fuels and Lubricants Meeting and Exposition, Portland,Oreg., Oct. 10-13, 1988.

This phenomenon is caused, during operation of the engine at lowtemperature (in cold weather, for example), by an accumulation ofdeposits having a high viscosity at the interface between the intakevalve stem and the valve guide, in the indirect injection spark ignitionengines. The accumulation of such deposits on the valve stems hindersthe movements of the latter, the stems stick to the valve guides, whichcauses poor closing of the valves, causes sealing problems in thecombustion chamber, and can significantly affect the operation of theengine, and in particular can prevent it from starting in cold weather.This phenomenon of valve sticking is thus the cause of sealing problemsin the combustion chamber, responsible for a reduction in thecompression force and thus in the efficiency of the engines. In someextreme cases, the intake valve, which has remained open due to theaccumulation of the deposits, can collide with the piston. Thiscollision can then lead to deformation of the valve and/or of the valvestem and thus to the breakdown of the engine.

In a way known per se, a distinction is made between different types ofdeposits on the intake valves of indirect injection spark ignitionengines. These types of deposits are well known to auto mechanics, andthe appearance of some is dependent on the solutions for the treatmentof the others.

On the one hand, a first type of deposit consists of those which form athigh temperature on the intake valves of indirect injection sparkignition engines during the use of a fuel not containing a detergentadditive. These deposits are in particular made up of carbon-basedresidues related to the phenomenon of coking and can also comprisedeposits of soap and/or lacquering type. These deposits are generallytreated by the use of detergent additive added to the fuel(additive-treated fuel).

On the other hand, a second type of deposit consists of viscousdeposits, mentioned above, which form at low temperature, typically at atemperature of less than or equal to 5° C., and which appear on thestems of the intake valves of indirect injection spark ignition enginesduring the use of additive-treated fuels, thus causing the phenomenon ofvalve sticking described above. Low-temperature deposits are veryparticularly formed during certain operating conditions of the engine,such as, for example, short trips in cold weather. Under theseconditions, the engine does not have the time to reach its normaloperating temperature. This operating mode can be characterized by thefact that the temperature of the coolant rarely reaches more than 60°C., indeed even does not exceed 30° C.

Thus, the additivation of the fuel for the treatment and the preventionof the deposits which form at high temperature can cause the appearanceof viscous deposits at low temperature.

As set out in the abovementioned publication (SAE Technical Paper SeriesNo. 881643), the composition of the gasoline and of the additives whichit contains have a very major influence on the phenomena of valvesticking. In particular, the detergent additives conventionallyincorporated in gasolines in order to keep the valves clean at hightemperature have paradoxically proved to promote phenomena of valvesticking at low temperature. In a way known per se, the problem of valvesticking does not occur or occurs very slightly when a fuel devoid ofdetergent additives is used. Furthermore, the abovementioned publicationshows that polymeric additives, capable of being employed in gasolinesand/or motor oils, are known to be agents which promote valve sticking.

In order to reduce the deposits on the intake valves and to preventthese sticking phenomena, the application 0 870 819 proposes to add, tothe gasoline composition, additives obtained by a Mannich condensationreaction starting from a hydroxyaromatic compound substituted by a groupderived from a polyolefin having a number-average molecular weightranging from 500 to 3000 and by a C1 to C4 alkyl group; from analiphatic polyamine having a single primary or secondary amino group;and from an aldehyde; with a molar ratio of the aldehyde to the amine ofless than or equal to 1.2. This document additionally recommendsincorporating the additive within a carrier oil, in particular ofpoly(oxyalkylene) type, which is described as reinforcing theeffectiveness of the additive in minimizing or reducing deposits on theintake valves and/or the sticking of said valves.

This is because it is known to use a carrier oil containing detergentsin order to limit or reduce the formation of deposits formed at hightemperatures on the intake valves, while limiting the phenomenon ofvalve sticking. However, this solution proves to be expensive, and theaim is as far as possible to avoid the use of such an oil, or to reducethe amount thereof as much as possible.

The application U.S. Pat. No. 7,291,681 proposes the use, as detergentadditive for gasolines of polyisobuteneamines having a number-averagemolecular weight Mn ranging from 500 to 1500 and a polydispersity indexMw/Mn of less than 1.4.

Example 2 of this document presents the results of comparative testsrelating to the evaluation of the performance qualities of several fuelswith or without additives, in terms of deposits on the valves, on theone hand, and valve sticking, on the other hand. These results confirmthat an additive-free fuel does not cause valve sticking but generatessignificant deposits on the valves. These results also show that thespecific polyisobuteneneamines according to this document make itpossible to very significantly reduce the deposits on the valves whilepreventing the latter from sticking, provided, however, that they areintroduced in combination with a carrier oil (poly(l-butene oxide)). Inthe absence of such an oil, a phenomenon of valve sticking occurs.

The solutions proposed in the prior art are therefore not entirelysatisfactory.

Thus, there exists a need to propose a solution for additivation of thefuel which makes it possible to effectively prevent deposits which canappear on the intake valves and to thus avoid phenomena of sticking ofthese at low temperature.

In particular, there remains a need to propose fuel additives which canbe used in the engines of indirect injection spark ignition engineswhich make it possible both to prevent (“keep-clean” effect) and toreduce (“clean-up” effect) in an effective way the deposits on thevalves at low temperature.

These solutions should, if possible, also make it possible to avoid theuse of a carrier oil, such as, for example, a poly(oxyalkylene) oil.

SUBJECT MATTER OF THE INVENTION

The applicant company has discovered that copolymers formed fromspecific units as described below have noteworthy properties when theyare used as additive in fuels for indirect injection spark ignitionengines. Used in these fuels, the copolymers according to the inventionmake it possible to keep the intake valves clean, preventing thephenomena of sticking of the latter at low temperature.

“Low temperature” denotes, in the present patent application, atemperature of less than or equal to 5° C., preferably of less than orequal to 0° C. and more preferentially still of less than or equal to−5° C.

These copolymers exhibit the additional advantage of being able to beused without a carrier oil.

These properties are all the more unexpected as the prior art teaches,on the contrary, that fuel additives and a fortiori polymeric compoundspromote the phenomena of valve sticking.

The additional advantages associated with the use in fuels for sparkignition engines of the copolymers according to the invention are:

-   -   optimum operation of the engine, in particular at low        temperature,    -   reduction in the fuel consumption,    -   better handling of the vehicle,    -   reduced emissions of pollutants, and    -   savings due to less maintenance of the engine.

A subject matter of the present invention is the use, in order toprevent deposits at low temperature on the fuel intake valves inindirect injection spark ignition engines, of one or more copolymer(s)comprising:

-   -    at least one unit of following formula (I):

-   -   in which:    -   u=0 or 1,    -   R₁′ represents a hydrogen atom or a methyl group,    -   E represents —O— or —N(Z)— or —O—CO— or —CO—O— or —NH—CO— or        —CO—NH—, with Z representing H or a C₁ to C₆ alkyl group,    -   G represents a group chosen from a C₁ to C₃₄ alkyl group, an        aromatic nucleus, an aralkyl group comprising at least one        aromatic nucleus and at least one C₁ to C₃₄ alkyl group, and    -    at least one unit of following formula (II):

-   -   in which:    -   v=0 or 1,    -   R₁″ is chosen from the hydrogen atom and the methyl group,    -   Q is chosen from the oxygen atom and an —NR′— group with R′        being chosen from a hydrogen atom and C₁ to C₁₂ hydrocarbon        chains,    -   R represents a C₁ to C₃₄ hydrocarbon chain which can also        contain one or more nitrogen and/or oxygen atoms and/or carbonyl        groups, which is substituted by at least one amino group        comprising a primary, secondary or tertiary amine or quaternary        ammonium functional group, and optionally one or more hydroxyl        groups.

By “preventing the deposits on the fuel intake valves” is understood tomean that the use according to the invention makes it possible to avoidthe formation of deposits on said valves (“keep-clean” effect), but alsoto reduce the amount of deposits when such deposits are already present(“clean-up” effect).

As indicated above, the deposits treated in the context of the presentinvention are those which form at low temperature, that is to say at atemperature of less than or equal to 5° C., preferably of less than orequal to 0° C. and more preferentially still of less than or equal to−5° C. These are viscous deposits located at the stems of the valves andwhich are capable of causing phenomena of valve sticking.

Preferentially, the group G of the formula (I) is chosen from a C4 toC34 alkyl group, an aromatic nucleus, an aralkyl group comprising atleast one aromatic nucleus and at least one C1 to C34 alkyl group,preferably a C4 to C34 alkyl group.

According to a first alternative form, the group G of the formula (I) isan aralkyl group comprising at least one aromatic nucleus and at leastone C4 to C30 alkyl group.

According to a second preferred alternative form, the group G of theformula (I) is a C4 to C34 alkyl group.

According to a first embodiment, the group E of the formula (I) ischosen from: —O— and —N(Z)—, with Z representing H or a C1 to C6 alkylgroup.

According to a second embodiment, the group E of the formula (I) ischosen from: —O—CO— and —NH—CO—; preferably the group E is the —O—CO—group, it being understood that the group E=—O—CO— is connected to thevinyl carbon by the oxygen atom and that the group E=—NH—CO— isconnected to the vinyl carbon by the nitrogen atom.

According to a third embodiment, the group E of the formula (I) ischosen from: —CO—O— and —CO—NH—; preferably the group E is the —CO—O—group, it being understood that the group E is connected to the vinylcarbon by the carbon atom.

According to a first alternative form, the amino group present in thegroup R of the formula (II) is chosen from the groups having at leastone amine, imine, amidine, guanidine, aminoguanidine or biguanidinefunctional group, such as alkylamines, polyalkylenepolyamines,polyalkylenimines, alkylimines, alkylamidines, alkylguanidines andalkylbiguanidines, it being possible for the alkyl substituent to belinear or branched, cyclic or acyclic, and preferably having from 1 to34 carbon atoms, more preferentially from 1 to 12 carbon atoms, and thequaternized forms of these groups.

According to a second alternative form, said amino group present in thegroup R of the formula (II) is chosen from monocyclic or polycyclicheterocyclic groups, having from 3 to 34 atoms, preferably from 5 to 12atoms, more preferentially from 6 to 10 atoms, and at least one nitrogenatom, it being understood that the polycyclic heterocyclic groups have,optionally, fused rings. The number of atoms includes the heteroatoms.Fused rings is understood to mean rings having at least two atoms incommon. The heterocyclic groups can additionally comprise an oxygen atomand/or a carbonyl group and/or one or more unsaturations.

Mention may be made, as example of a heterocyclic amino group, of thefollowing radicals: triazole, aminotriazole, pyrrolidone, piperidine,imidazole, morpholine, isoxazole, oxazole, indole and the quaternizedforms of these radicals, said radical preferably being connected to thehydrocarbon chain by a nitrogen atom.

According to a preferred embodiment, the group R of the formula (II) isrepresented:

-   -    when v has the value 1, by the formula (V):

L-R′₂  (V)

-   -    when v has the value 0, by the formula (V) or the formula (V):

L-R′₂  (V)

L-  (V)

-   -   in which formulae (V) and (V′):    -    R₂′ is chosen from C₁ to C₃₄ hydrocarbon chains, optionally        substituted by at least one hydroxyl group, and    -    L is chosen from the group consisting of:        -   the following groups:            -   amine: —NH₂; —NHR_(a), —NR_(a)R_(b);            -   imine: —HC═NH; —HC═NR_(a); —N═CH₂, —N═CR_(a)H;                —N═CR_(a)R_(b); amidine: —(C═NH)—NH₂; —(C═NH)—NR_(a)H;                —(C═NH)—NR_(a)R_(b); —(C═NR_(a))—NH₂;                —(C═NR_(a))—NR_(b)H; —(C═NR_(a))—NR_(b)R_(c);                —N═CH(NH₂); —N═CR_(a)(NH₂); —N═CH(NR_(a)H);                —N═CR_(a)(NR_(a)H); —N═CH(NR_(a)R_(b));                —N═CR_(a)(NR_(b)R_(c));            -   guanidine: —NH—(C═NH)—NH₂; —NH—(C═NH)—NHR_(a);                —N═C(NH₂)₂; —N═C(NR_(a)H)₂; —N═C(NR_(a)R_(b))₂;                —N═C(NR_(a)H)(NR_(b)H);            -   aminoguanidine: —NH—(C═NH)—NH—NH₂;                —NH—(C═NH)—NH—NHR_(a); —N═C(NH₂)(NH—NH₂);                —N═C(NR_(a)H)(NH—NH₂); —N═C(NR_(a)H)(NR_(a)—NH₂);                —N═C(NR_(a)R_(b))(NH—NH₂);                —N═C(NR_(a)R_(b))(NR_(a)—NH₂);            -   biguanidine: —NH—(C═NH)—NH—(C═NH)—NH₂;                —NH—(C═NH)—NH—(C═NH)—NHR_(a); —N═C(NH₂)—NH—(C═NH)—NH₂;                —N═C(NH₂)—NH—(C═NR_(a))—NH₂;                —N═C(NH₂)—NH—(C═NH)—NR_(a)H;                —N═C(NH₂)—NH—(C═NR_(a))—NR_(b)H;                —N═C(NH₂)—NH—(C═NH)—NR_(a)R_(b);                —N═C(NH₂)—NH—(C═NR_(a))—NR_(b)R_(c);                —N═C(NR_(a)H)—NH—(C═NH)—NH₂;                —N═C(NR_(a)H)—NH—(C═NR_(b))—NH₂;                —N═C(NR_(a)H)—NH—(C═NH)—NR_(b)H;                —N═C(NR_(a)H)—NH—(C═NR_(b))—NR_(c)H;                —N═C(NR_(a)H)—NH—(C═NH)—NR_(b)R_(c);                —N═C(NR_(a)H)—NH—(C═NR_(b))—NR_(c)R_(d);                —N═C(NR_(a)R_(b))—NH—(C═NH)—NH₂;                —N═C(NR_(a)R_(b))—NH—(C═NR_(c))—NH₂;                —N═C(NR_(a)R_(b))—NH—(C═NH)—NR_(c)H;                —N═C(NR_(a)R_(b))—NH—(C═NR_(c))—NR_(d)H;                —N═C(NR_(a)R_(b))—NH—(C═NH)—NR_(c)R_(d);                —N═C(NR_(a)R_(b))—NH—(C═NR_(c))—NR_(d)R_(e);            -   the quaternized forms of the above groups, when these                contain at least one quaternizable nitrogen atom; and        -   polyamine and polyalkylenepolyamine groups, in particular            those of formulae —NH—(R_(f)—NH)_(k)—H;            —NH—(R_(f)—NH)_(k)—R_(a);        -   with R_(a), R_(b), R_(c), R_(d) and R_(e) representing,            independently of one another, a C₁-C₃₄, preferably C₁-C₁₂,            alkyl group, optionally comprising one or more NH₂            functional groups and one or more —NH— bridges;        -   R_(f) represents a C₁-C₆, preferably C₂-C₄, alkyl group; k            represents an integer ranging from 1 to 20, preferably from            2 to 12.

Mention may be made, as example of polyamine and polyalkylenepolyaminegroups, of: ethylenediamine, diethylenetriamine, triethylenetetramine ortetraethylenepentamine.

The quaternary ammonium functional group(s) optionally present in thegroup R of the units of formula (II) can be chosen in particular frompyrrolinium, pyridinium, imidazolium, triazolium, triazinium, oxazoliumand isoxazolium quaternary ammoniums.

According to an alternative form, the quaternary ammonium functionalgroup(s) is (are) chosen from trialkylammonium, iminium, amidinium,formamidinium, guanidinium and biguanidinium quaternary ammoniums, andpreferably trialkylammonium quaternary ammonium.

According to a preferred embodiment, the quaternary ammonium functionalgroup(s) optionally present in the group R of the units of formula (II)is (are) represented by one of the following formulae (III) and (IV):

in which:

-   -   X⁻ is chosen from hydroxide or halide ions and organic anions,        preferably organic anions, R₂ is chosen from C₁ to C₃₄        hydrocarbon chains, optionally substituted by at least one        hydroxyl group,    -   R₃, R₄ and R₅ are identical or different and are chosen        independently from C₁ to C₁₈ hydrocarbon chains, it being        understood that the R₃, R₄ and R₅ groups can contain one or more        groups chosen from: a nitrogen atom, an oxygen atom and a        carbonyl group and that the R₃, R₄ and R₅ groups can be        connected together in pairs to form one or more rings,    -   R₆ and R₇ are identical or different and are chosen        independently from C₁ to C₁₈ hydrocarbon chains, it being        understood that the R₆ and R₇ groups can contain one or more        groups chosen from: a nitrogen atom, an oxygen atom and a        carbonyl group and that the R₆ and R₇ groups can be connected        together to form a ring.    -   According to a particularly preferred embodiment, the quaternary        ammonium functional group(s) optionally present in the group R        of the units of formula (II) is (are) represented by the above        formula (III), in which:    -   X⁻ is chosen from organic anions, preferably conjugate bases of        carboxylic acids,    -   R₂ is chosen from C₁ to C₃₄ hydrocarbon chains, preferably C₁ to        C₁₈ alkyl groups,    -   R₃, R₄ and R₅ are identical or different and are chosen        independently from C₁ to C₁₈ hydrocarbon chains, optionally        substituted by at least one hydroxyl group, it being understood        that at least one of the R₃, R₄ and R₅ groups contains one or        more hydroxyl group(s).

According to a preferred embodiment, the copolymer employed in thepresent invention contains units of formula (II) comprising a group Rcontaining at least one quaternary ammonium functional group.

According to a particularly preferred embodiment, from 5 mol % to 95 mol% of the units of formula (II) of the copolymer comprise, in the groupR, at least one quaternary ammonium functional group.

In this embodiment, the units of formula (II) in which the group R doesnot comprise a quaternary ammonium functional group comprise, in thegroup R, at least one amino group comprising a primary, secondary ortertiary amine functional group. These units represent from 5 mol % to95 mol % of the units of formula (II) of the copolymer according to theinvention.

According to an advantageous alternative form of this embodiment, thecopolymer comprises a first type of units of formula (II) in which thegroups R comprise at least one quaternizable nitrogen atom and a secondtype of units of formula (II) obtained by quaternization of the units ofthe first type.

The copolymer employed in the present invention can be obtained bycopolymerization of at least:

-   -    a nonpolar monomer (m_(a)) corresponding to the following        formula (VII):

-   -   in which:    -   R₁′, u, E and G are as defined above, and    -    one or more polar monomers (m_(b)) corresponding to the        following formula (VIII):

-   -    in which:    -   R₁″, v, Q and R are as defined above.

According to a preferred embodiment, from 5 mol % to 95 mol % of thepolar monomers (mb) comprise a group R containing at least onequaternary ammonium functional group.

According to another embodiment, the copolymer employed in the inventionis obtained by copolymerization of at least:

-   -    a nonpolar monomer (m_(a)) corresponding to the following        formula (VII):

in which:

-   -   R₁′, u, E and G are as defined above, and    -    a polar monomer (m_(b)) corresponding to the following formula        (VIII):

-   -   in which:    -   R₁″, v and Q and are as defined above,    -   and R represents a C₁ to C₃₄ hydrocarbon chain which can also        contain one or more nitrogen and/or oxygen atoms and/or carbonyl        groups, which is substituted by at least one amino group        comprising a primary, secondary or tertiary amine functional        group, and optionally one or more hydroxyl groups,    -   the copolymerization being followed by a partial quaternization        of the amino groups of the units resulting from the monomer        (m_(b)).

“Partial quaternization” is understood to mean a quaternization of 5 mol% to 95 mol % of the amino groups of the units resulting from themonomer (mb). This quaternization of said amino groups implies that theycomprise at least one quaternizable nitrogen atom.

According to a preferred embodiment, the monomer (ma) is chosen from C1to C34 alkyl acrylates and C1 to C34 alkyl methacrylates.

According to a preferred embodiment, the copolymer according to theinvention is chosen from block copolymers and random copolymers, andpreferably the copolymer according to the invention is a blockcopolymer.

Preferably, the copolymer according to the invention is a blockcopolymer comprising:

-   -    a block A corresponding to the following formula (XI):

-   -   in which:    -   p is an integer ranging from 2 to 100, preferably ranging from 5        to 80, preferably ranging from 10 to 70, more preferentially        ranging from 20 to 60,    -   R₁′, u, E and G are as defined above, and    -    a block B corresponding to the following formula (XII):

-   -   in which:    -   n is an integer ranging from 2 to 50, preferably from 3 to 40,        more preferentially from 4 to 20, more preferentially still from        5 to 10,    -   R₁″, v, Q and R are as defined above.

According to a preferred embodiment, from 5 mol % to 95 mol % of theunits of the block B comprise a group R containing at least onequaternary ammonium functional group.

Preferably, the block copolymer comprises at least:

-   -   a block A consisting of a chain of structural units derived from        one or more nonpolar monomers chosen from nonpolar monomers        (m_(a)) of formula (VII), and    -   a block B consisting of a chain of structural units derived from        one or more polar monomers chosen from polar monomers (m_(b)) of        formula (VIII).

According to a first embodiment, the block copolymer comprises at least:

-   -   the block A consisting of a chain of structural units derived        from a single nonpolar monomer chosen from nonpolar monomers        (m_(a)) of formula (VII), and    -   the block B consisting of a chain of structural units derived        from a single polar monomer chosen from polar monomers (mb) of        formula (VIII).

In this first embodiment, according to an advantageous alternative form,the block copolymer comprises at least:

-   -   the block A consisting of a chain of structural units derived        from a C1-C34 alkyl (meth)acrylate monomer (ma), and    -   the block B consisting of a chain of structural units derived        from an alkyl (meth)acrylate or alkyl(meth)acrylamide monomer        (mb), the alkyl radical of which consists of a C1 to C34        hydrocarbon chain substituted by at least one amino group chosen        from primary, secondary or tertiary amines and quaternary        ammoniums, and optionally one or more hydroxyl groups.

According to a second embodiment, the block copolymer comprises atleast:

-   -   the block A consisting of a chain of structural units derived        from a single nonpolar monomer chosen from nonpolar monomers        (ma) of formula (VII), and    -   the block B consisting of a chain of structural units, 5 mol %        to 95 mol % of which are derived from a single polar monomer        chosen from polar monomers (mb) of formula (VIII) in which the        group R contains at least one quaternary ammonium functional        group, and 5 mol % to 95 mol % of which are derived from a        single polar monomer chosen from polar monomers (mb) of        formula (VIII) in which the group R does not contain a        quaternary ammonium functional group and comprises at least one        amino group comprising a primary, secondary or tertiary amine        functional group.

In this second embodiment, according to an advantageous alternativeform, the block copolymer comprises at least:

-   -   the block A consisting of a chain of structural units derived        from a C1-C34 alkyl (meth)acrylate monomer (ma), and    -   the block B consisting of a chain of structural units derived        from alkyl (meth)acrylate or alkyl(meth)acrylamide monomers        (mb), 5 mol % to 95 mol % of which have an alkyl radical        consisting of a C1 to C34 hydrocarbon chain substituted by a        quaternary ammonium group and optionally one or more hydroxyl        groups, and 5 mol % to 95 mol % of which have an alkyl radical        consisting of a C1 to C34 hydrocarbon chain substituted by a        group chosen from primary, secondary or tertiary amines,        preferably tertiary amines, and optionally one or more hydroxyl        groups.

Preferably, the number of monomer equivalents (ma) of the block A isfrom 2 to 100 moles.

Preferably, the number of monomer equivalents (mb) of the block B isfrom 2 to 50 moles.

Preferably, the copolymer comprises at least one sequence of blocks AB,ABA or BAB, where said blocks A and B are linked together without thepresence of an intermediate block of different chemical nature.

Preferentially, the block copolymer is obtained by block polymerization,optionally followed by one or more post-functionalizations.

The copolymer according to the invention is used by incorporating it ina fuel composition, to which it can be added alone or in the form of afuel concentrate comprising one or more copolymer(s) according to theinvention as defined above, as a mixture with an organic liquid, saidorganic liquid being inert with regard to said copolymer(s) and misciblewith said fuel.

The fuel compositions, in which the copolymer according to the inventioncan be used, can result from one or more sources chosen from the groupconsisting of mineral, animal, vegetable and synthetic sources.

Preferably, the fuel is chosen from hydrocarbon fuels, fuels which arenot essentially hydrocarbon fuels, and their mixtures.

Advantageously, the hydrocarbon fuel is chosen from gasolines.

Preferably, the copolymer according to the invention is used in the fuelcomposition at a minimum content of 5 ppm.

According to a preferred embodiment, said copolymer is used to preventthe formation of deposits at low temperature on the stems of the intakevalves, and more particularly to prevent said valves from sticking atlow temperature.

The invention additionally relates to a process for keeping clean, atlow temperature, the fuel intake valves in an indirect injection sparkignition engine comprising at least the following stages:

-   -   the preparation of a fuel composition by additivation of a fuel        with a copolymer as described above, then    -   the injection of said fuel composition into the spark ignition        engine.

DETAILED DESCRIPTION

Other advantages and characteristics will emerge more clearly from thedescription which will follow. The specific embodiments of the inventionare given as nonlimiting examples.

For reasons of simplicity, the following terms are employed in thepresent description:

-   -   alkyl (meth)acrylate to denote an alkyl acrylate or an alkyl        methacrylate;    -   alkyl(meth)acrylamide to denote an alkylacrylamide or an        alkylmethacrylamide;

and

-   -   quaternary ammonium to denote a quaternary ammonium salt.

The copolymer:

The copolymer used in the present invention comprises:

-   -    at least one unit of following formula (I):

-   -   in which:    -   u=0 or 1,    -   R₁′ represents a hydrogen atom or a methyl group,    -   E represents —O— or —N(Z)— or —O—CO— or —CO—O— or —NH—CO— or        —CO—NH—, with Z representing H or a C₁ to C₆ alkyl group,    -   G represents a group chosen from a C₁ to C₃₄ alkyl group, an        aromatic nucleus, an aralkyl group comprising at least one        aromatic nucleus and at least one C₁ to C₃₄ alkyl group, and    -    at least one unit of following formula (II):

-   -   in which:    -   v=0 or 1,

R₁″ is chosen from the hydrogen atom and the methyl group,

-   -   Q is chosen from the oxygen atom and an —NR′— group with R′        being chosen from a hydrogen atom and C₁ to C₁₂ hydrocarbon        chains,    -   R represents a C₁ to C₃₄ hydrocarbon chain which can also        contain one or more nitrogen and/or oxygen atoms and/or carbonyl        groups, which is substituted by at least one amino group        comprising a primary, secondary or tertiary amine or quaternary        ammonium functional group, and optionally one or more hydroxyl        groups.

According to a specific embodiment, the copolymer comprises only unitsof formula (I) and units of formula (II).

According to a specific embodiment, the copolymer is chosen from blockcopolymers and random copolymers.

According to a particularly preferred embodiment, the copolymer is ablock copolymer.

According to a first alternative form, the unit of formula (I) is chosenfrom those satisfying u=0.

Preferentially, and according to this first alternative form, thecopolymer is a block copolymer.

According to another alternative form, the unit of formula (I) is chosenfrom those satisfying u=1.

The group E of formula (I) is chosen from:

-   -   E=—O—,    -   E=—N(Z)—, with Z represents H or a linear or branched, cyclic or        acyclic, preferably acyclic, C₁ to C₆ alkyl group,    -   E=—O—CO—, it being understood that E is then connected to the        vinyl carbon by the oxygen atom,    -   E=—CO—O—, it being understood that E is then connected to the        vinyl carbon by the carbon atom,    -   E=—NH—CO—, and    -   E=—CO—NH—.

According to a first embodiment, the group E of the formula (I) ischosen from: —O— and —N(Z)—, with Z representing H or a C1 to C6 alkylgroup.

According to a second embodiment, the group E of the formula (I) ischosen from: —O—CO— and —NH—CO—, it being understood that the groupE=—O—CO— is connected to the vinyl carbon by the oxygen atom and thatthe group E=—NH—CO— is connected to the vinyl carbon by the nitrogenatom.

According to this same embodiment, the group E of the formula (I) ispreferably the —O—CO— group, it being understood that the —O—CO— groupis connected to the vinyl carbon by the oxygen atom.

According to a third embodiment, the group E of the formula (I) ischosen from: —CO—O— and —CO—NH—, it being understood that the group E isconnected to the vinyl carbon by the carbon atom.

According to this same implementational third, the group E of theformula (I) is preferably the —CO—O— group, it being understood that the—CO—O— group is connected to the vinyl carbon by the carbon atom.

According to a preferred embodiment, the unit of formula (I) is suchthat u=1, and the group E is a —CO—O— group, E being connected to thevinyl carbon by the carbon atom.

The group (G) of the formula (I) can be a C1 to C34 alkyl group,preferably a C4 to C34, preferably C4 to C30, more preferentially C6 toC24, more preferentially still C8 to C18 alkyl radical. The alkylradical is a linear or branched, cyclic or acyclic, preferably acyclic,radical. This alkyl radical can comprise a linear or branched part and acyclic part.

The group (G) of the formula (I) is advantageously an acyclic C1 to C34alkyl, preferably a linear or branched, preferably branched, C4 to C34,preferably C4 to C30, more preferentially C6 to C24, more preferentiallystill C8 to C18 alkyl radical.

Mention may be made, without limitation, of alkyl groups, such as butyl,octyl, decyl, dodecyl, 2-ethylhexyl, isooctyl, isodecyl and isododecyl.

The group (G) of the formula (I) can also be an aromatic nucleus,preferably a phenyl or aryl group. Mention may be made, among aromaticgroups, without limitation, of the phenyl or naphthyl group, preferablythe phenyl group.

The group (G) of the formula (I) can, according to another preferredalternative form, be an aralkyl comprising at least one aromatic nucleusand at least one C1 to C34 alkyl group. Preferably, according to thisalternative form, the group (G) is an aralkyl comprising at least onearomatic nucleus and one or more C4 to C34, preferably C4 to C30, morepreferentially C6 to C24, more preferentially still C8 to C18 alkylgroups.

The aromatic nucleus can be monosubstituted or be substituted on severalof its carbon atoms. Preferably, the aromatic nucleus ismonosubstituted.

The C1 to C34 alkyl group can be in the ortho, meta or para position onthe aromatic nucleus, preferably in the para position.

The alkyl radical is a linear or branched, cyclic or acyclic, preferablyacyclic, radical.

The alkyl radical is preferably a linear or branched, preferablybranched, acyclic radical.

The aromatic nucleus can be directly connected to the group E or to thevinyl carbon but it can also be connected to it via an alkylsubstituent.

Mention may be made, by way of example of group G, of a benzyl groupsubstituted in the para position by a C4 to C34, preferably C4 to C30,alkyl group.

Preferably, according to this alternative form, the group (G) of theformula (I) is an aralkyl comprising at least one aromatic nucleus andat least one C4 to C34, preferably C4 to C 30, more preferentially C6 toC24, more preferentially still C8 to C18 alkyl group.

According to a specific embodiment, the group Q of the formula (II) isthe oxygen atom.

According to a first alternative form, the amino group present in thegroup R of the formula (II) is chosen from the groups having at leastone amine, imine, amidine, guanidine, aminoguanidine or biguanidinefunctional group, such as alkylamines, polyalkylenepolyamines,polyalkylenimines, alkylimines, alkylamidines, alkylguanidines andalkylbiguanidines, it being possible for the alkyl substituent to belinear or branched, cyclic or acyclic, and preferably having from 1 to34 carbon atoms, more preferentially from 1 to 12 carbon atoms, and thequaternized forms of these groups.

According to a second alternative form, the amino group present in thegroup R of the formula (II) is chosen from monocyclic or polycyclicheterocyclic groups, having from 3 to 34 atoms, preferably from 5 to 12atoms, more preferentially from 6 to 10 atoms, and at least one nitrogenatom, it being understood that the polycyclic heterocyclic groups have,optionally, fused rings. The number of atoms includes the heteroatoms.Fused rings is understood to mean rings having at least two atoms incommon. The heterocyclic groups can additionally comprise an oxygen atomand/or a carbonyl group and/or one or more unsaturations.

Mention may be made, as example of a heterocyclic amino group, of thefollowing radicals: triazole, aminotriazole, pyrrolidone, piperidine,imidazole, morpholine, isoxazole, oxazole, indole and the quaternizedforms of these radicals, said radical preferably being connected to thehydrocarbon chain by a nitrogen atom.

According to a preferred embodiment, the group R of the formula (II) isrepresented:

-   -    when v has the value 1, by the following formula (V):

L-R′₂  (V)

-   -    when v has the value 0, by one of the following formulae (V)        and (V):

L-R′₂  (V)

L-  (V)

-   -   in which formulae (V) and (V′):    -    R₂′ is chosen from cyclic or acyclic, linear or branched, C₁ to        C₃₄, preferably C₁ to C₁₈, more preferentially C₁ to C₈, more        preferentially still C₂ to C₄ hydrocarbon chains, optionally        substituted by at least one hydroxyl group; preferably, R₂′ is        chosen from alkyl groups, optionally substituted by at least one        hydroxyl group, and    -    L is chosen from the group consisting of:        -   the following groups:            -   amine: —NH2; —NHR_(a), —NR_(a)R_(b);            -   imine: —HC═NH; —HC═NR_(a); —N═CH₂, —N═CR_(a)H;                —N═CR_(a)R_(b);            -   amidine: —(C═NH)—NH₂; —(C═NH)—NR_(a)H;                —(C═NH)—NR_(a)R_(b); —(C═NR_(a))—NH₂;                —(C═NR_(a))—NR_(b)H; —(C═NR_(a))—NR_(b)R_(c);                —N═CH(NH₂); —N═CR_(a)(NH₂); —N═CH(NR_(a)H);                —N═CR_(a)(NR_(a)H); —N═CH(NR_(a)R_(b));                —N═CR_(a)(NR_(b)R_(c));            -   guanidine: —NH—(C═NH)—NH₂; —NH—(C═NH)—NHR_(a);                —N═C(NH₂)₂; —N═C(NR_(a)H)₂; —N═C(NR_(a)R_(b))₂;                —N═C(NR_(a)H)(NR_(b)H);            -   aminoguanidine: —NH—(C═NH)—NH—NH₂;                —NH—(C═NH)—NH—NHR_(a); —N═C(NH₂)(NH—NH₂);                —N═C(NR_(a)H)(NH—NH₂); —N═C(NR_(a)H)(NR—NH₂);                —N═C(NR_(a)R_(b))(NH—NH₂);                —N═C(NR_(a)R_(b))(NR_(a)—NH₂);            -   biguanidine: —NH—(C═NH)—NH—(C═NH)—NH₂;                —NH—(C═NH)—NH—(C═NH)—NHR_(a); —N═C(NH₂)—NH—(C═NH)—NH₂;                —N═C(NH₂)—NH—(C═NR_(a))—NH₂;                —N═C(NH₂)—NH—(C═NH)—NR_(a)H;                —N═C(NH₂)—NH—(C═NR_(a))—NR_(b)H;                —N═C(NH₂)—NH—(C═NH)—NR_(a)R_(b);                —N═C(NH₂)—NH—(C═NR_(a))—NR_(b)R_(c);                —N═C(NR_(a)H)—NH—(C═NH)—NH₂;                —N═C(NR_(a)H)—NH—(C═NR_(b))—NH₂;                —N═C(NR_(a)H)—NH—(C═NH)—NR_(b)H;                —N═C(NR_(a)H)—NH—(C═NR_(b))—NR_(c)H;                —N═C(NR_(a)H)—NH—(C═NH)—NR_(b)R_(c);                —N═C(NR_(a)H)—NH—(C═NR_(b))—NR_(c)R_(d);                —N═C(NR_(a)R_(b))—NH—(C═NH)—NH₂;                —N═C(NR_(a)R_(b))—NH—(C═NR_(c))—NH₂;                —N═C(NR_(a)R_(b))—NH—(C═NH)—NR_(c)H;                —N═C(NR_(a)R_(b))—NH—(C═NR_(c))—NR_(d)H;                —N═C(NR_(a)R_(b))—NH—(C═NH)—NR_(c)R_(d);                —N═C(NR_(a)R_(b))—NH—(C═NR_(c))—NR_(d)R_(e);            -   the quaternized forms of the above groups, when these                contain at least one quaternizable nitrogen atom; and        -   polyamine and polyalkylenepolyamine groups, in particular            those of formulae —NH—(R_(f)—NH)_(k)—H;            —NH—(R_(f)—NH)_(k)—R_(a);        -   with R_(a), R_(b), R_(c), R_(d) and R_(e) representing,            independently of one another, a C₁-C₃₄, preferably C₁-C₁₂,            alkyl group, optionally comprising one or more NH₂            functional groups and one or more —NH— bridges;        -   R_(f) representing a C₁-C₆, preferably C₂-C₄, alkyl group; k            represents an integer ranging from 1 to 20, preferably from            2 to 12.

Mention may be made, as example of polyamine and polyalkylenepolyaminegroups, of: ethylenediamine, diethylenetriamine, triethylenetetramine ortetraethylenepentamine.

According to a specific embodiment, the R2′ group is chosen from linearor branched acyclic C1 to C34, preferably C1 to C18, more preferentiallyC1 to C8, more preferentially still C2 to C4 alkyl groups, which can besubstituted by at least one hydroxyl group.

According to a preferred embodiment, the group R of the formula (II)comprising at least one amino group comprising a primary, secondary ortertiary amine functional group is represented by the formula (V) inwhich L is chosen from the groups: —NH2, —NHRa, —NRaRb, with Ra and Rbas defined above, and more preferably from the tertiary amine groups—NRaRb.

According to a preferred embodiment, the group R comprising at least onequaternary ammonium functional group is represented by one of thefollowing formulas (III) and (IV):

-   -   in which:    -   X⁻ is chosen from hydroxide or halide ions and organic anions,        in particular the acetate ion,    -   R₂ is chosen from cyclic or acyclic, linear or branched, C₁ to        C₃₄, preferably C₁ to C₁₈, more preferentially C₁ to C₈, more        preferentially still C₂ to C₄ hydrocarbon chains, optionally        substituted by at least one hydroxyl group; preferably, R₂′ is        chosen from alkyl groups, optionally substituted by at least one        hydroxyl group,    -   R₃, R₄ and R₅ are identical or different and are chosen        independently from linear or branched, cyclic or acyclic, C₁ to        C₁₈, preferably C₁ to C₁₂, hydrocarbon chains, it being        understood that the R₃, R₄ and R₅ alkyl groups can contain one        or more nitrogen and/or oxygen atoms and/or carbonyl groups and        can be connected together in pairs to form one or more rings,    -   R₆ and R₇ are identical or different and are chosen        independently from linear or branched, cyclic or acyclic, C₁ to        C₁₈, preferably C₁ to C₁₂, hydrocarbon chains, it being        understood that the R₆ and R₇ groups can contain one or more        nitrogen and/or oxygen atoms and/or carbonyl groups and can be        connected together to form a ring.

The nitrogen and/or oxygen atom(s) can be present in the R₃, R₄ and R₅groups in the form of ether bridges or amine bridges or in the form ofan amine or hydroxyl substituent.

The organic anions of the X− group are advantageously conjugate bases oforganic acids, preferably conjugate bases of carboxylic acids, inparticular acids chosen from cyclic or acyclic monocarboxylic orpolycarboxylic acids. Preferably, the organic anions of the X− group arechosen from conjugate bases of saturated acyclic or aromatic cycliccarboxylic acids. Mention will be made, by way of example, of methanoicacid, acetic acid, adipic acid, oxalic acid, malonic acid, succinicacid, citric acid, benzoic acid, phthalic acid, isophthalic acid andterephthalic acid.

According to a specific embodiment, the R2 group is chosen from linearor branched acyclic C1 to C34, preferably C1 to C18, more preferentiallyC1 to C8, more preferentially still C2 to C4 alkyl groups, substitutedby at least one hydroxyl group.

Advantageously, the group R comprising at least one quaternary ammoniumfunctional group is represented by the formula (III), in which:

-   -   X− is chosen from organic anions, preferably conjugate bases of        carboxylic acids,    -   R2 is chosen from C1 to C34 hydrocarbon chains, preferably C1 to        C18 alkyl groups,    -   R3, R4 and R5 are identical or different and are chosen        independently from 01 to C18 hydrocarbon chains, optionally        substituted by at least one hydroxyl group, it being understood        that at least one of the R3, R4 and R5 groups contains one or        more hydroxyl group(s).

According to a preferred embodiment, the copolymer used in the presentinvention contains units of formula (II) in which the group R containsat least one quaternary ammonium functional group.

The preferred groups R containing a quaternary ammonium functional groupare those described above.

According to a particularly preferred embodiment, from 5 mol % to 95 mol% of the units of formula (II) of the copolymer comprise, in the groupR, at least one quaternary ammonium functional group.

In this embodiment, the proportion in moles of the units of formula (II)in which the group R comprises at least one quaternary ammoniumfunctional group, also referred to below as degree of quaternization ofthe units of formula (II), advantageously represents from 10% to 90%,more preferentially from 20% to 80% and more preferentially still from40% to 60%, with respect to the total molar amount of units of formula(II) in the copolymer.

According to a very particularly preferred embodiment, the degree ofquaternization of the units of formula (II) ranges from 45% to 55%, withrespect to the total molar amount of units of formula (II).

In this embodiment, the units of formula (II) in which the group R doesnot comprise a quaternary ammonium functional group comprise at leastone amino group comprising a primary, secondary or tertiary aminefunctional group. The preferred groups R containing a primary, secondaryor tertiary amine functional group are those described above.

These units represent from 5 mol % to 95 mol % of the total molar amountof the units of formula (II) of the copolymer according to theinvention, preferably from 10 mol % to 90 mol %, more preferentiallyfrom 20 mol % to 80 mol %, more preferentially still from 40 mol % to 60mol % and better still from 45 mol % to 55 mol %.

In this embodiment, the quaternary ammonium functional groups of thegroup R of the formula (II) can advantageously be obtained by partialquaternization of one of the groups of formulae (V) and (V′) above,these containing at least one quaternizable nitrogen atom.

The quaternary ammonium functional groups can in particular be obtainedby partial quaternization of at least one amine, imine, amidine,guanidine, aminoguanidine or biguanidine functional group; or else of aheterocyclic group having from 3 to 34 atoms and at least one nitrogenatom.

Particularly preferably, the quaternary ammonium functional groups ofthe group R are obtained by partial quaternization of tertiary aminefunctional groups.

According to a specific embodiment, the unit of formula (I) of thecopolymer employed in the invention is obtained from a nonpolar monomer(ma).

Preferably, the nonpolar monomer (ma) corresponds to the followingformula (VII):

-   -   in which:    -   R₁′, E, G and u are as defined above; the preferred alternative        forms of R₁′, E, G and u according to the formula (I) as are        defined above are also preferred alternative forms of the        formula (VII).

Advantageously, the R1′ group is a hydrogen atom.

When the group E of the nonpolar monomer (ma) is the —O—CO— group, itbeing understood that the —O—CO— group is connected to the vinyl carbonby the oxygen atom, the monomer (ma) is preferably chosen from vinyl C1to C34, preferably C4 to C30, more preferentially C6 to C24, morepreferentially C8 to C22 alkyl esters. The alkyl radical of the vinylalkyl ester is linear or branched, cyclic or acyclic, preferablyacyclic.

Mention may be made, among the vinyl alkyl ester monomers, for example,of vinyl octanoate, vinyl decanoate, vinyl dodecanoate, vinyltetradecanoate, vinyl hexadecanoate, vinyl octadecanoate, vinyldocosanoate or vinyl 2-ethylhexanoate.

When the group E of the nonpolar monomer (ma) is the —CO—O— group, itbeing understood that the —CO—O— group is connected to the vinyl carbonby the carbon atom, the monomer (ma) is preferably chosen from C1 toC34, preferably C4 to C30, more preferentially C6 to C24, morepreferentially C8 to C22 alkyl acrylates or methacrylates. The alkylradical of the acrylate or methacrylate is linear or branched, cyclic oracyclic, preferably acyclic.

Mention may be made, among the alkyl (meth)acrylates capable of beingused, without limitation, of: n-octyl acrylate, n-octyl methacrylate,n-decyl acrylate, n-decyl methacrylate, n-dodecyl acrylate, n-dodecylmethacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctylacrylate, isooctyl methacrylate, isodecyl acrylate or isodecylmethacrylate.

According to a specific embodiment, the unit of formula (II) of thecopolymer employed in the present invention is obtained from polarmonomers (mb) chosen from those of formula (VIII):

-   -   in which:    -   R₁″, v, Q and R are as defined above; the preferred alternative        forms of R₁″, Q and R according to the formula (II) as are        defined above are also preferred alternative forms of the        formula (VIII).

According to a first alternative form of this embodiment, from 5 mol %to 95 mol % of the polar monomers (mb) comprise a group R containing atleast one quaternary ammonium functional group.

In this alternative form, preferably from 5 mol % to 95 mol % of thepolar monomers (mb) comprise a quaternary ammonium functional group andare represented by at least one of the following formulae (IX) and(IX′):

-   -   and from 5 mol % to 95 mol % of the polar monomers (m_(b)) do        not comprise a quaternary ammonium functional group and are        represented by the following formula (X):

-   -   in which formulae (IX), (IX′) and (X):    -   R₁″, v and Q are as defined above; the preferred alternative        forms of R₁″ and Q according to formula (II) as defined above        are also preferred alternative forms of the formulae (IX), (IX′)        and (X);    -   X⁻, R₂, R₃, R₄, R₅, R₆ and R₇ are as defined above; the        preferred alternative forms of X⁻,    -   R₂, R₃, R₄, R₅, R₆ and R₇ according to the formulae (III)        and (IV) as defined above are also preferred alternative forms        of the formulae (IX) and (IX′).    -   R′₂ and L are as defined above; the preferred alternative forms        of R′2 and L according to the formula (V) are also preferred        alternative forms of the formula (X).

According to a specific embodiment, the unit of formula (II) of thecopolymer employed in the present invention is obtained from polarmonomers (m_(b)) chosen from those of formula (VIII):

-   -   in which:    -   R₁″, v and Q are as defined above, the preferred alternative        forms of R₁″ and Q according to the formula (II) as are defined        above are also preferred alternative forms of the formula        (VIII), and    -   R represents a C₁ to C₃₄ hydrocarbon chain which can also        contain one or more nitrogen and/or oxygen atoms and/or carbonyl        groups, which is substituted by at least one amino group        comprising a primary, secondary or tertiary amine functional        group, and optionally one or more hydroxyl groups,    -   the copolymerization of the monomer (m_(b)) being followed by a        partial quaternization of the quaternizable amino groups, for 5        mol % to 95 mol % of the units resulting from said monomer        (m_(b)).

This embodiment is preferred.

According to a specific embodiment, the copolymer can be obtained bycopolymerization of at least one nonpolar monomer (ma) and at least onepolar monomer (mb) as are described above.

According to a specific preferred embodiment, the copolymer is obtainedsolely from nonpolar monomers (ma) and polar monomers (mb).

The copolymer can be prepared according to any known polymerizationprocess. The various polymerization techniques and conditions are widelydescribed in the literature and fall within the general knowledge of aperson skilled in the art.

According to a specific embodiment, the copolymer is a block copolymercomprising at least one block A and at least one block B.

The block A corresponds to the following formula (XI):

-   -   in which:    -   p is an integer ranging from 2 to 100, preferably from 5 to 80,        preferably from 10 to 70, more preferentially from 20 to 60,    -   R₁′, E, G and u are as defined above; the preferred alternative        forms of R₁′, E, G and u according to the formula (I) as are        defined above are also preferred alternative forms of the        formula (XI).

The block B corresponds to the following formula (XII):

-   -   in which:    -   v=0 or 1,    -   n is an integer ranging from 2 to 50, preferably from 3 to 40,        more preferentially from 4 to 20, more preferentially still from        5 to 10,    -   R₁″, Q and R are as defined above; the preferred alternative        forms of R₁″, Q and R according to the formula (II) as are        defined above are also preferred alternative forms of the        formula (XII).

According to a preferred embodiment, from 5 mol % to 95 mol % of theunits of the block B comprise a group R containing at least onequaternary ammonium functional group.

In this embodiment, the block B preferably comprises:

-   -    from 5 mol % to 95 mol % of units comprising a quaternary        ammonium functional group and corresponding to at least one of        the following formulae (XIII) and (XIII′):

-   -    and from 5 mol % to 95 mol % of units not comprising a        quaternary ammonium functional group and corresponding to the        following formula (XIV):

-   -   in which formulae (XIII), (XIII′) and (XIV):    -   Q, R₁″, n and v are as described above; the preferred        alternative forms of Q and R₁″ according to the formula (II) as        defined above are also preferred alternative forms of the        formulae (XIII), (XIII′) and (XIV),    -   X⁻, R₂, R₃, R₄, R₅, R₆ and R₇ are as defined above; the        preferred alternative forms of X⁻,    -   R₂, R₃, R₄, R₅, R₆ and R₇ according to the formulae (III)        and (IV) as defined above are also preferred alternative forms        of the formulae (XIII) and (XIII′),    -   R′₂ and L are as defined above; the preferred alternative forms        of R′₂ and L according to the formula (V) are also preferred        alternative forms of the formula (XIV).

The amino groups of the block B comprising quaternary ammoniumfunctional groups are advantageously chosen from trialkylammonium,iminium, amidinium, formamidinium, guanidinium and biguanidiniumquaternary ammoniums, preferably trialkylammonium quaternary ammoniums.

The amino groups of the block B comprising quaternary ammoniumfunctional groups can also be chosen from heterocyclic compoundscontaining at least one nitrogen atom, in particular chosen frompyrrolinium, pyridinium, imidazolium, triazolium, triazinium, oxazoliumand isoxazolium quaternary ammoniums.

The amino groups of the block B comprising quaternary ammoniumfunctional groups are particularly preferably trialkylammoniumquaternary groups.

According to a preferred alternative form, at least one of the alkylgroups of the quaternary ammonium of the block B is substituted by ahydroxyl group.

According to a particularly preferred embodiment, the block B comprisesfrom 5 mol % to 95 mol % of units corresponding to the formula (XIII):

-   -   in which:    -   R₁″ is chosen from the hydrogen atom and the methyl group,    -   Q is chosen from the oxygen atom and the —NR′— group, with R′        being chosen from a hydrogen atom and C₁ to C₁₂ hydrocarbon        chains,    -   X⁻ is chosen from organic anions, preferably conjugate bases of        carboxylic acids,    -   R₂ is chosen from C₁ to C₃₄ hydrocarbon chains, preferably C₁ to        C₁₈ alkyl groups,    -   R₃, R₄ and R₅ are identical or different and are chosen        independently from C₁ to C₁₈ hydrocarbon chains, optionally        substituted by at least one hydroxyl group, it being understood        that at least one of the R₃, R₄ and R₅ groups contains at least        one hydroxyl group.

The distribution within the block B of the units, the group R of whichcomprises at least one quaternary ammonium functional group, withrespect to the other units of the block B, can be of any type, and inparticular random, statistical or block. Preferably, this distributionis of random type.

According to a specific embodiment, the block A consists of a chain ofstructural units derived from at least one monomer (ma) as describedabove.

According to a specific embodiment, the block B consists of a chain ofstructural units derived from monomers (mb) as described above.

According to a specific embodiment, the block A consists of a chain ofstructural units derived from an alkyl acrylate or alkyl methacrylatemonomer (ma) and the block B corresponds to the formula (XII) describedabove.

According to a specific embodiment, the block copolymer is obtained bycopolymerization of at least the alkyl (meth)acrylate monomer (ma) andat least the monomer(s) (mb) described above.

It is understood that it would not be departing from the invention ifthe copolymer (a) according to the invention were obtained from monomersother than (ma) and (mb), insofar as the final copolymer corresponds tothat of the invention, that is to say comprises units of formula (I) andunits of formula (II) as are described above. For example, it would notbe departing from the invention if the copolymer were obtained bycopolymerization of monomers other than (ma) and (mb), followed by apostfunctionalization.

For example, the blocks deriving from a nonpolar monomer (ma) can beobtained from vinyl alcohol or acrylic acid, respectively bytransesterification or amidation reaction.

For example, the quaternary ammonium units of the block B can beobtained by postfunctionalization of the intermediate units (Mi)resulting from the polymerization of an intermediate (meth)acrylate or(meth)acrylamide monomer (m_(i)), of formulae:

-   -   with    -   Q and R₁″ are as described above,    -   R₈ is chosen from C₁ to C₃₂ hydrocarbon chains,    -   R₉ is chosen from hydrogen and C₁ to C₆ alkyl groups,    -   said postfunctionalization corresponding to the reaction of said        intermediate unit (M_(i)) with a tertiary amine NR₃R₄R₅ or        R₆N═R₇ where R₃, R₄, R₅, R₆ and R₇ are as defined above in the        formulae (Ill) and (IV).

The copolymer according to the invention can also be obtained bypostfunctionalization of an intermediate block polymer, comprising atleast one intermediate block containing units (Mi) and at least oneblock A as described above.

According to a particularly preferred embodiment, the block B of formula(XII) is obtained by quaternization, according to any known method, offrom 5 mol % to 95 mol % of the units of an intermediate block Bicomprising a single unit of formula (XII) in which the groups R containa tertiary amine group of formula NR3R4R5 or R6N═R7 in which R3, R4, R5,R6 and R7 are as defined above.

The quaternization stage can be carried out before the copolymerizationreaction, on an intermediate monomer carrying the tertiary amine, forexample by reaction with an alkyl halide or an epoxide (oxirane)according to any known process, optionally followed by a anion-exchangereaction.

The quaternization stage can also be carried out bypostfunctionalization of an intermediate polymer carrying the tertiaryamine, for example, by reaction with an alkyl halide, optionallyfollowed by an anion-exchange reaction. Mention may be made, by way ofexample of quaternization, of a postfunctionalization reaction of anintermediate polymer carrying the tertiary amine, by reaction with anepoxide (oxirane) according to any known process.

It is preferred to copolymerize intermediate monomers carrying atertiary amine functional group and then, in a second stage, tofunctionalize the intermediate copolymer obtained by quaternization ofthe tertiary amine present in the intermediate copolymer, rather than tocopolymerize monomers which are already quaternized.

In addition, it will be preferable to carry out the quaternizationinvolving an epoxide.

The block copolymer can be obtained by block polymerization, preferablyby controlled block polymerization, optionally followed by one or morepostfunctionalizations.

According to a specific embodiment, the block copolymer described aboveis obtained by controlled block polymerization. The polymerization isadvantageously chosen from controlled radical polymerization; forexample atom transfer radical polymerization (ATRP); nitroxide-mediatedradical polymerization (NMP); degenerative transfer processes, such asdegenerative iodine transfer polymerization (ITRP: iodine transferradical polymerization) or reversible addition-fragmentationchain-transfer radical polymerization (RAFT: reversibleaddition-fragmentation chain transfer); polymerizations derived fromATRP, such as polymerizations using initiators for continuous activatorregeneration (ICAR) or using activators regenerated by electron transfer(ARGET).

Mention will be made, by way of example, of the publication“Macromolecular engineering by atom transfer radical polymerization”,JACS, 136, 6513-6533 (2014), which describes a controlled blockpolymerization process for forming block copolymers.

Mention may be made, by way of example, for NMP, of the identificationby C. J. Hawker of an alkoxyamine capable of acting as a unimolecularagent, providing both the reactive initiating radical and theintermediate nitroxide radical in stable form (C. J. Hawker, J. Am.Chem. Soc., 1994, 116, 11185). Hawker has also developed a universal NMPinitiator (D. Benoit et al., J. Am. Chem. Soc., 1999, 121, 3904).

Reversible addition-fragmentation chain transfer (RAFT) radicalpolymerization is a living radical polymerization technique. The RAFTtechnique was discovered in 1998 par by the Australian scientificresearch organization CSIRO (J. Chiefari et al., Macromolecules, 1998,31, 5559). The RAFT technique very rapidly became the subject ofintensive research studies by the scientific community since it makespossible the synthesis of macromolecules exhibiting complexarchitectures, in particular block, grafted, comb or else star-branchedstructures, while making it possible to control the molecular weight ofthe macromolecules obtained (G. Moad et al., Aust. J. Chem., 2005, 58,379). RAFT polymerization can be applied to a very wide range of vinylmonomers and under various experimental conditions, including in thepreparation of water-soluble materials (C. L. McCormick et al., Acc.Chem. Res., 2004, 37, 312). The RAFT process includes the conventionalradical polymerization of a substituted monomer in the presence of asuitable chain-transfer agent (CTA or RAFT agent). The RAFT agentscommonly used comprise thiocarbonylthio compounds, such as dithioesters(J. Chiefari et al., Macromolecules, 1998, 31, 5559), dithiocarbamates(R. T. A. Mayadunne et al., Macromolecules, 1999, 32, 6977; M. Destaracet al., Macromol. Rapid. Commun., 2000, 21, 1035), trithiocarbonates (R.T. A. Mayadunne et al., Macromolecules, 2000, 33, 243) and xanthates (R.Francis et al., Macromolecules, 2000, 33, 4699), which perform thepolymerization by a reversible chain-transfer process. The use of asuitable RAFT agent makes possible the synthesis of polymers exhibitinga high degree of functionality and exhibiting a narrow molecular weightdistribution, that is to say a low polydispersity index (PDI).

Mention may be made, by way of example of description of RAFT radicalpolymerization, of the following documents: WO 1998/01478, WO1999/31144, WO 2001/77198, WO 2005/00319 and WO 2005/000924.

The controlled block polymerization is typically carried out in asolvent, under an inert atmosphere, at a reaction temperature generallyranging from 0° C. to 200° C., preferably from 50° C. to 130° C. Thesolvent can be chosen from polar solvents, in particular ethers, such asanisole (methoxybenzene) or tetrahydrofuran, or nonpolar solvents, inparticular paraffins, cycloparaffins, aromatics and alkylaromaticshaving from 1 to 19 carbon atoms, for example benzene, toluene,cyclohexane, methylcyclohexane, n-butene, n-hexane, n-heptane and thelike.

For the atom transfer radical polymerization (ATRP), the reaction isgenerally carried out under vacuum in the presence of an initiator, of aligand and of a catalyst. Mention may be made, by way of example ofligand, of N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA),1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), 2,2′-bipyridine(BPY) and tris(2-pyridylmethyl)amine (TPMA). Mention may be made, by wayof example of catalyst, of: CuX, CuX2, with X=Cl or Br, and complexesbased on ruthenium Ru2+/Ru3+.

The ATRP polymerization is preferably carried out in a solvent chosenfrom polar solvents.

According to the controlled block polymerization technique, it can alsobe envisaged to work under pressure.

The numbers of equivalents of nonpolar monomer (ma) of the block A andof polar monomer (mb) of the block B reacted during the polymerizationreaction can be identical or different.

“Number of equivalents” is understood to mean the amounts (in moles) ofmaterial of the monomers (ma) of the block A and of the monomers (mb) ofthe block B employed during the polymerization reaction.

The number of equivalents of nonpolar monomer (ma) of the block A ispreferably from 2 to 100 eq, preferably from 5 to 80 eq, preferably from10 to 70 eq and more preferentially from 20 to 60 eq.

The number of equivalents of polar monomers (mb) of the block B ispreferably from 2 to 50 eq, preferably from 3 to 40 eq, morepreferentially from 4 to 20 eq and more preferentially still from 5 to10 eq.

The number of equivalents of monomer (ma) of the block A isadvantageously greater than or equal to that of the monomers (mb) of theblock B.

Preferably, when the group E of the nonpolar monomer (ma) is a —CO—O—group, E being connected to the vinyl carbon by the carbon atom, thenumber of equivalents of monomer (ma) of the block A is between 20 and60 moles, and G is chosen from C4 to C30 hydrocarbon chains.

More preferentially still, when the group E of the nonpolar monomer (ma)is a —CO—O— group, E being connected to the vinyl carbon by the carbonatom, the number of equivalents of monomer (ma) of the block A isbetween 20 and 60 moles, and G is chosen from C4 to C30 hydrocarbonchains, and the copolymer has a number-average molecular weight (Mn)ranging from 1000 and 10 000 g·mol-1.

In addition, the weight-average molar mass Mw of the block A or of theblock B is preferably less than or equal to 15 000 g·mol.-1, morepreferentially less than or equal to 10 000 g·mol.-1.

The block copolymer advantageously comprises at least one sequence ofblocks AB, ABA or BAB where said blocks A and B are linked togetherwithout the presence of an intermediate block of different chemicalnature.

Other blocks can optionally be present in the block copolymer describedabove insofar as these blocks do not fundamentally change the nature ofthe block copolymer. Nevertheless, block copolymers containing onlyblocks A and B will be preferred.

Advantageously, the blocks A and B represent at least 70% by weight,preferably at least 90% by weight, more preferentially at least 95% byweight, more preferentially still at least 99% by weight of the blockcopolymer.

According to a specific embodiment, the block copolymer is a diblockcopolymer.

According to another specific embodiment, the block copolymer is atriblock copolymer having alternating blocks comprising two blocks A andone block B (ABA) or comprising two blocks B and one block A (BAB).

According to a specific embodiment, the block copolymer also comprisesan end chain I consisting of a cyclic or acyclic, saturated orunsaturated, linear or branched, C1 to C32, preferably C4 to C24, morepreferentially C10 to C24 hydrocarbon chain.

Cyclic hydrocarbon chain is understood to mean a hydrocarbon chain, atleast a part of which is cyclic, in particular aromatic. This definitiondoes not exclude hydrocarbon chains comprising both an acyclic part anda cyclic part.

The end chain I can comprise an aromatic hydrocarbon chain, for examplea benzene chain, and/or a saturated and acyclic, linear or branched,hydrocarbon chain, in particular an alkyl chain.

The end chain I is preferably chosen from alkyl chains, preferablylinear alkyl chains, more preferentially alkyl chains of at least 4carbon atoms, more preferentially still of at least 12 carbon atoms.

For the ATRP polymerization, the end chain I is located in the endposition of the block copolymer. It can be introduced into the blockcopolymer by virtue of the polymerization initiator. Thus, the end chainI can advantageously constitute at least a part of the polymerizationinitiator and is positioned within the polymerization initiator in orderto make it possible to introduce, during the first stage of initiationof the polymerization, the end chain I in the end position of the blockcopolymer.

The polymerization initiator is, for example, chosen from thefree-radical initiators employed in the ATRP polymerization process.These free-radical initiators well known to a person skilled in the artare in particular described in the paper “Atom transfer radicalpolymerization: current status and future perspectives”, Macromolecules,45, 4015-4039, 2012.

The polymerization initiator is, for example, chosen from carboxylicacid alkyl esters substituted by a halide, preferably a bromine in thealpha position, for example ethyl 2-bromopropionate, ethylα-bromoisobutyrate, benzyl chloride or bromide, ethylα-bromophenylacetate and chloroethylbenzene. Thus, for example, ethyl2-bromopropionate can make it possible to introduce into the copolymerthe end chain I in the form of a C2 alkyl chain and benzyl bromide inthe form of a benzyl group.

For the RAFT polymerization, the transfer agent can conventionally beremoved from the copolymer at the end of polymerization according to anyknown process.

According to an alternative form, the end chain I can also be obtainedin the copolymer by RAFT polymerization according to the methodsdescribed in the paper by Moad, G. et al., Australian Journal ofChemistry, 2012, 65, 985-1076. For example, the end chain I can, forexample, be modified by aminolysis when a transfer agent is used inorder to give a thiol functional group. Mention may be made, by way ofexample, of transfer agents of thiocarbonylthio, dithiocarbonate,xanthate, dithiocarbamate and trithiocarbonate type, for exampleS,S0-dibenzyl trithiocarbonate (DBTTC), S,S-bis(α,α′-dimethyl-α″-aceticacid) trithiocarbonate (BDMAT) or 2-cyano-2-propyl benzodithioate (CPD).

According to a known process, the transfer agent can be cleaved at theend of polymerization by reacting a cleaving agent, such as C2-C6alkylamines; the end functional group of the copolymer can in this casebe a thiol —SH group.

According to another process described in the patent EP 1 751 194, thesulfur of the copolymer obtained by RAFT polymerization introduced bythe sulfur-based transfer agent, such as thiocarbonylthio,dithiocarbonate, xanthate, dithiocarbamate and trithiocarbonate, can beconverted in order to remove the sulfur from the copolymer.

According to a specific embodiment, the block copolymer is a diblockcopolymer. The block copolymer structure can be of the IAB or IBA type,advantageously IAB type. The end chain I can be directly connected tothe block A or B according to the structure IAB or IBA respectively orcan be connected via a bonding group, for example an ester, amide, amineor ether functional group. The bonding group then forms a bridge betweenthe end chain I and the block A or B.

According to a specific embodiment, the block copolymer can also befunctionalized at the chain end according to any known process, inparticular by hydrolysis, aminolysis and/or nucleophilic substitution.

Aminolysis is understood to mean any chemical reaction in which amolecule is split into two parts by reaction of a molecule of ammonia orof an amine. A general example of aminolysis consists in replacing ahalogen of an alkyl group by reaction with an amine, with elimination ofhydrogen halide. Aminolysis can be used, for example, for an ATRPpolymerization which produces a copolymer having a halide in the endposition or for a RAFT polymerization in order to convert the thio,dithio or trithio bond introduced into the copolymer by the RAFTtransfer agent into a thiol functional group.

An end chain I′ can thus be introduced by postfunctionalization of theblock copolymer obtained by controlled block polymerization of themonomers ma and mb described above.

The end chain I′ advantageously comprises a linear or branched, cyclicor acyclic, C1 to C32, preferably C1 to C24, more preferentially C1 toC10 hydrocarbon chain, more preferentially still an alkyl group,optionally substituted by one or more groups containing at least oneheteroatom chosen from N and O, preferably N.

For an ATRP polymerization using a metal halide as catalyst, thisfunctionalization can, for example, be carried out by treating thecopolymer IAB or IBA obtained by ATRP with a primary C1 to C32alkylamine or a C1 to C32 alcohol under mild conditions in order not tomodify the functional groups present on the blocks A, B and I.

Use

The present invention consists in using the copolymers described abovein order to prevent the deposits which form at low temperature on thefuel intake valves in indirect injection spark ignition engines.

To this end, the copolymer is incorporated in a liquid fuel for a sparkignition engine and in particular a fuel chosen from gasolines.

The copolymer(s) according to the invention is (are) used in the fuelcomposition in a total content of at least 5 ppm by weight, preferablyof at least 10 ppm, more preferentially at a content of 10 to 5000 ppm,more preferentially still of 20 to 2000 ppm and better still of 50 to1000 ppm.

In particular, the use of the copolymers according to the invention istargeted at keeping the valves clean, by preventing the valves fromsticking at low temperature.

The liquid fuel advantageously results from one or more sources chosenfrom the group consisting of mineral, animal, plant and syntheticsources. Oil will preferably be chosen as mineral source.

The liquid fuel is preferably chosen from hydrocarbon fuels and fuelswhich are not essentially hydrocarbon fuels, alone or as a mixture.

Hydrocarbon fuel is understood to mean a fuel formed of one or morecompounds consisting solely of carbon and hydrogen.

Fuel which is not essentially hydrocarbon fuel is understood to mean afuel formed of one or more compounds which are not essentially formed ofcarbon and hydrogen, that is to say which also contain other atoms, inparticular oxygen atoms.

Hydrocarbon fuels comprise in particular light distillates having aboiling point in the range of the gasolines. These distillates can, forexample, be chosen from the distillates obtained by direct distillationof crude hydrocarbons, vacuum distillates, hydrotreated distillates,distillates resulting from the catalytic cracking and/or from thehydrocracking of vacuum distillates, distillates resulting fromconversion processes of ARDS (atmospheric residue desulfurization)and/or visbreaking type, or distillates resulting from the upgrading ofFischer-Tropsch fractions.

In other words, the hydrocarbon fuel is chosen from gasolines.

Gasolines in particular comprise any commercially available fuelcomposition for a spark ignition engine. Mention may be made, by way ofrepresentative example, of the gasolines corresponding to the standardNF EN 228. Gasolines generally have octane numbers which aresufficiently high to prevent the phenomenon of knocking. Typically, thefuels of gasoline type sold in Europe, in accordance with the standardNF EN 228, have a motor octane number (MON) of greater than 85 and aresearch octane number (RON) of a minimum of 95. Fuels of gasoline typegenerally have an RON ranging from 90 to 100 and an MON ranging from 80to 90, the RON and MON values being measured according to the standardASTM D 2699-86 or D 2700-86.

Fuels which are not essentially hydrocarbon fuels comprise in particularoxygen-based compounds, for example distillates resulting from the BTL(biomass to liquid) conversion of plant and/or animal biomass, takenalone or in combination; biofuels, for example plant and/or animal oilsand/or ester oils; biodiesels of animal and/or plant origin andbioethanols.

The mixtures of hydrocarbon fuel and of fuel which is not essentiallyhydrocarbon fuel are typically gasolines of Ex type.

Gasoline of Ex type for a spark ignition engine is understood to mean agasoline fuel which contains x % (v/v) of oxygen-based compounds,generally ethanol, bioethanol and/or ethyl tert-butyl ether (ETBE).

The sulfur content of the liquid fuel is preferably less than or equalto 50 ppm, indeed even less than 10 ppm and advantageously sulfur-free.

The use of the copolymer(s) as described above as additives in theliquid fuel exhibits the advantage of preventing the phenomena of valvesticking.

The level of valve sticking can be determined according to thestandardized engine test method CEC F 16-T-96. This method consists inrunning a spark ignition gasoline engine according to operating pointsdescribed in the method, in then halting it and gradually bringing thetemperature from +90° C. down to +5° C. over 10 h (temperature of thecoolant), then maintaining it at +5° C. for an additional 5 h. Onconclusion of this, cylinder compression measurements are carried out,which reflect the quality of the sealing in the combustion chamber. Ifthe reference compression pressure is not achieved for one or morecylinders, this reflects the presence of a phenomenon of valve sticking.

Thus, according to a particularly preferred embodiment, a subject matterof the invention is the use of the copolymer as described above forpreventing deposits at low temperature on fuel intake valves and inparticular for preventing the sticking of said valves, which isdetermined according to the standardized method CEC F 16-T-96.

In order to demonstrate and quantify the valve sticking, it is alsopossible to employ the method described in the abovementionedpublication SAE Technical Paper Series No. 881643 (see method describedon page 3 and in Appendix 1 of this publication).

According to a specific embodiment, the use of said copolymeradditionally makes it possible to reduce the fuel consumption of thespark ignition engine.

The copolymer(s) as described above can be used alone or as a mixturewith other additives, for example in the form of an additiveconcentrate.

The copolymers according to the invention can be added to the liquidfuel within a refinery and/or be incorporated downstream of the refineryand/or optionally as a mixture with other additives in the form of anadditive concentrate, also known according to common use as “additivepackage”.

According to one embodiment, the copolymer according to the invention isused as a mixture with an organic liquid which is inert with regard tosaid copolymer and miscible with the fuel composition, intended tofacilitate the incorporation of said copolymer in the composition.

According to a specific embodiment, a concentrate for fuel comprises oneor more copolymers as described above, as a mixture with an organicliquid.

The organic liquid is inert with regard to the block copolymer(s)according to the invention and miscible in the liquid fuel describedabove. Miscible is understood to mean the fact that the copolymer andthe organic liquid form a solution or a dispersion so as to facilitatethe mixing of the copolymer according to the invention in the liquidfuels according to conventional processes for the additivation of fuels.

The organic liquid can, for example, be chosen from aromatic hydrocarbonsolvents, such as the solvent sold under the name Solvesso, alcohols,ethers and other oxygen-based compounds, and paraffinic solvents, suchas hexane, pentane or isoparaffins, alone or as a mixture.

The concentrate can advantageously comprise a total amount ofcopolymer(s) according to the invention ranging from 5% to 99% byweight, preferably from 10% to 80% by weight, more preferentially from25% to 70% by weight.

The concentrate can typically comprise from 1% to 95% by weight,preferably from 20% to 90% by weight, more preferentially from 30% to75% by weight of organic liquid, the remainder corresponding to thecopolymer according to the invention, it being understood that theconcentrate can comprise one or more copolymers as described above.

Generally, when the copolymer according to the invention is a blockcopolymer, its solubility in the organic liquids and the liquid fuelswhich are described above depends in particular on the weight-averageand number-average molar masses, respectively Mw and Mn, of thecopolymer. The average molar masses Mw and Mn of the copolymer accordingto the invention will be chosen so that the copolymer is soluble in theliquid fuel and/or the organic liquid of the concentrate for which it isintended.

The average molar masses Mw and Mn of the copolymer according to theinvention can also have an influence on the effectiveness of thecopolymer as additive in fuels. The average molar masses Mw and Mn willthus be chosen so as to optimize the effect of the copolymer accordingto the invention, in particular the effect of preventing valve sticking.

The average molar masses Mw and Mn can be optimized by routine testsopen to a person skilled in the art.

According to a specific embodiment, the copolymer according to theinvention advantageously exhibits a weight-average molar mass (Mw)ranging from 500 to 30 000 g·mol-1, preferably from 1000 to 10 000g·mol-1, more preferentially less than or equal to 4000 g·mol-1, and/ora number-average molar mass (Mn) ranging from 500 to 15 000 g·mol-1,preferably from 1000 to 10 000 g·mol-1, more preferentially less than orequal to 4000 g·mol-1. The number-average and weight-average molarmasses are measured by size exclusion chromatography (SEC). Theoperating conditions for the SEC, in particular the choice of thesolvent, will be chosen as a function of the chemical functional groupspresent within the block copolymer.

The molar ratio and/or the ratio by weight between the polar monomer(mb) and the nonpolar monomer (ma) and/or between block A and B in theblock copolymer described above will also be chosen so that the blockcopolymer is soluble in the fuel and/or the organic liquid of theconcentrate for which it is intended. Likewise, this ratio can beoptimized as a function of the fuel and/or of the organic liquid so asto obtain the best effect of prevention of the valve sticking.

The molar ratio and/or the ratio by weight can be optimized by routinetests open to a person skilled in the art.

According to a specific embodiment, the molar ratio of the nonpolarmonomer (ma) to the polar monomer (mb), or of the block A to the block Bas molar percentage of the nonpolar monomer (ma) of the block A to thepolar monomer (mb) of the block B, is preferably between 95:5 and 50:50,more preferentially between 90:10 and 75:25, more preferentially stillbetween 85:15 and 70:30.

According to a specific embodiment, the copolymer according to theinvention is used in the form of an additive concentrate in combinationwith at least one other additive for internal combustion engine fuelother than the copolymers according to the invention described above.

The additive concentrate can typically comprise one or more otheradditives other than the copolymers according to the invention, chosenfrom detergent additives, corrosion inhibitors, antioxidants,dispersants, demulsifiers, biocides, reodorants, friction modifiers,lubricity additives, combustion aids (catalytic soot combustionpromoters), antisettling agents, antiwear agents and conductivitymodifiers.

Mention may in particular be made, among these additives, and withoutlimitation, of:

a) lubricity additives or antiwear agents, in particular (but notlimitingly) chosen from the group consisting of fatty acids and theirester or amide derivatives, in particular glyceryl monooleate, and mono-and polycyclic carboxylic acid derivatives. Examples of such additivesare given in the following documents: EP 680 506, EP 860 494,WO98/04656, EP 915 944, FR 2 772 783, FR 2 772 784;

b) detergent additives, in particular (but not limitingly) chosen fromthe group consisting of succinimides, polyetheramines and quaternaryammonium salts; for example, those described in the documents U.S. Pat.No. 4,171,959 and WO2006135881.

These other additives are generally added in an amount ranging from 10to 1000 ppm (each), preferably from 100 to 1000 ppm, by weight in thefuel composition.

The additive concentrate can also comprise an organic liquid asdescribed above, inert with regard to the additives described above andmiscible with the fuel composition, intended to facilitate theincorporation of the additives in the composition.

The invention additionally relates to a process for keeping clean, atlow temperature, the fuel intake valves in an indirect injection sparkignition engine comprising at least the following stages:

-   -   the preparation of a fuel composition by additivation of a fuel        with a copolymer as described above, then    -   the injection of said fuel composition into the spark ignition        engine.

The process for keeping clean (keep-clean) preferably comprises thesuccessive stages of:

-   -   1) determination of the additivation most suitable for the fuel,        said additivation corresponding to the selection of the block        copolymer(s) described above to be incorporated in combination,        optionally, with other fuel additives as described above, and        the determination of the degree of treatment necessary in order        to achieve a given specification relating to the cleanness of        the valves; then    -   2) incorporation in the fuel of the selected copolymer(s) at the        content determined in stage 1) and, optionally, of the other        fuel additives.

Alternatively, the copolymer according to the invention and the otheradditives, if appropriate, can be used in the form of a concentrate orof an additive concentrate as described above.

Stage 1) is carried out according to any known process and comes withinthe common practice in the field of the additivation of fuels. Thisstage involves defining at least one characteristic representative ofthe properties of the fuel composition in terms of effect on thecleanness of the valves.

The characteristic representative of the properties of the fuel can inparticular correspond to the appearance of phenomena of deposits on thevalves and/or to the appearance of phenomena of valve sticking, measuredin particular according to the standardized method CEC F-16-T96.

The amount of copolymer(s) according to the invention to be added to thefuel composition in order to achieve a given specification (stage 1)described above) will typically be determined by comparison with thefuel composition but without the copolymer(s) according to theinvention.

The amount of copolymer(s) according to the invention can also vary as afunction of the nature and of the origin of the fuel.

The process for keeping clean can also comprise an additional stage 3)after stage 2), of checking the target reached and/or of adjusting thedegree of additivation with the copolymer(s) according to the invention.

The examples below are targeted at illustrating the invention and shouldnot be interpreted as limiting the scope thereof.

Examples

1. Preparation of a Copolymer According to the Invention:

A quaternized EHMA/DAMEMA diblock copolymer in accordance with thepresent invention was synthesized by RAFT-type radical copolymerization,in accordance with the protocol described below.

EHMA Block A:

30.01 g (0.26 mmol) of 2-ethylhexyl methacrylate (EHMA), 2.89 g (13mmol) of 2-cyano-2-propyl benzodithioate and 35 ml of toluene areintroduced into a 250 ml round-bottomed flask. 210 mg (1.29 mmol) ofazobisisobutyronitrile (AIBN) are weighed out in a 20 ml round-bottomedflask and then dissolved in 4 ml of toluene. The two solutions aredegassed with nitrogen for 30 minutes. The solution containing the EHMAmonomer is heated to 80° C. When the temperature is reached, the AIBNsolution is added using a syringe purged with nitrogen beforehand. Thereaction medium is stirred at 80° C. for 24 h under an inert atmosphere(N2).

A 250 μl sample is withdrawn at t0 (immediately after addition of AIBN)and at tf (final t) in order to measure the content of residual monomersby HPLC and thus to deduce the conversion thereof.

Result: the ratio of areas of the peaks of the EHMA monomer gives aconversion of 98% (98% of the EHMA monomer was converted into polymer).

HPLC method employed: HPLC UltiMate 300 from Thermo Fisher. Thestationary phase of the device is a Symmetry Shield RP 18 column. Themobile phase is composed of two eluents, a first, the composition ofwhich is water/methanol with CH2O2 at pH 5; the second is composed ofmethanol with methanoic acid, also at pH 5. This mobile phase has a flowrate of 1 ml/min. The temperature of the oven is set at 40° C. Theinjection volume is 5 μl. The products are detected via a diode arraydetector.

Addition of the DAMEMA Block B:

10.22 g (88.7 mmol) of 2-(dimethylamino)ethyl methacrylate (DAMEMA) areweighed out in a 50 ml round-bottomed flask. 11 ml of toluene are added.Furthermore, 221 mg (1.35 mmol) of AIBN are weighed out in a 20 mlround-bottomed flask and then dissolved via 3 ml of toluene. Afterdegassing the two solutions with nitrogen for 30 minutes, the DAMEMAmonomer is added, via a syringe purged beforehand with nitrogen, to around-bottomed flask containing the EHMA block A heated to 80° C.; theAIBN solution is subsequently added. The reaction medium is stirred for24 h under an inert atmosphere (N2).

A 250 μl sample is withdrawn at t0 (immediately after addition of AIBN)and at tf (final t) in order to measure the content of residual monomersby HPLC (as described for the block A above) and thus to deduce theconversion thereof.

A sample is also withdrawn in order to determine, by 1H and 13C NMR, thenumbers of EHMA and DAMEMA units and the molar ratio of the twomonomers.

Analytical Methods:

The 1H and 13C NMR spectroscopy analyses were carried out in deuteratedchloroform CDCl3 with a Brüker Avance III 400 MHz NMR spectrometer(Larmor frequency of the 1H) operating under TopSpin 3.2: SEX 10 mm 13Cprobe with pulsed magnetic field z-gradient and 2H lock operating at300K and BBI 5 mm 1H probe with pulsed magnetic field z-gradient and 2Hlock operating at 300K. An external standard(1,2,4,5-tetrachloro-3-nitrobenzene) is used to carry out themeasurements.

Finally, the number-average molar masses Mn and weight-average molarmasses Mw, and also the dispersity index, which reflects the sizedispersity, PI (PI=Mw/Mn), were determined by GPC.

The GPC analyses were carried out in THF. In a typical analysis, 100 μlof a 0.5% w/w sample, filtered beforehand through a 0.45 μm Milliporefilter, are injected into Waters Styragel columns operating at 40° C.and 645 psi with a THF flow rate of 1 ml/min. The number-average molarmasses (Mn) were determined by RI (refractive index) detection fromcalibration curves constructed for PMMA standards. The analyses werecarried out within a column of Waters Styragel type with the refractiveindex as detector.

Results:

-   -   Conversion by HPLC: the ratio of the areas of the peaks of the        DAMEMA monomer gives a conversion of 97% (97% of the DAMEMA        monomer was converted into polymer).    -   Microstructure by ¹H et ¹³C NMR: based on the signals relating        to the chain ends, 17 EHMA units and 6 DAMEMA units are        determined. The molar relative composition: 71% EHMA, 29%        DAMEMA.    -   For the calculation of the number of units, by ¹³NMR, by setting        the integral of the signal at 132.3 ppm (associated with 1        aromatic CH group of the benzodithioate) at 1, an integral for        the broad unresolved peak of the OCH₂ groups (1C) of the EHMA        units (67.8-66.5 ppm) of 17 and an integral for the broad        unresolved peak of the NCH₂ groups (1C) of the DAMEMA units        (57.4-56.8 ppm) of 6, respectively, are obtained. Thus, if it is        assumed that all the polymer chains comprise the benzodithioate        group as end group, then the copolymer comprises 17 EHMA units        and 6 DAMEMA units.    -   GPC: M_(n)=2800 g/mol; M_(w)=3400 g/mol; PI=1.28.

Partial Quaternization of the Block B of the EHMA/DAMEMA DiblockCopolymer:

-   -   28.5 g of the solution of diblock polymer in toluene prepared        above are withdrawn and introduced into a 100 ml round-bottomed        flask. 10.5 g of butanol, 912 mg (12.6 mmol) of epoxybutane and        735 mg (12.2 mmol) of acetic acid are introduced. The mixture is        heated at 60° C. for 24 h, a Vigreux column on the        round-bottomed flask. At the end of the reaction, the mixture is        evaporated under reduced pressure.    -   After drying, a sample of the polymer is analyzed by ¹H and ¹³C        NMR.

Results:

-   -   The degree of quaternization of the block B (DAMEMA block) is 40        mol %.    -   The degree of quaternization is determined by ¹³C NMR. In ¹³C        NMR, the broad unresolved peak at approximately 70 ppm is        assigned to the CH₂ of the CH₂CHOHCH₂CH₃ group alpha to the        quaternized nitrogen atom. Based on the EHMA/DAMEMA molar        proportion (71/29), and by comparing the integral of the broad        unresolved peak at 70 ppm and the integral of the signal at 11        ppm (associated with one of the two CH₃ groups of the pendant        EHMA chain), the degree of quaternization is deduced therefrom,        which degree is 40%.

2. Comparative Tests:

2.1. Tests of Valve Sticking at Low Temperature:

The quaternized EHMA/DAMEMA copolymer obtained in example 1 (hereinafteradditive A) was compared with a detergent additive sold under the nameKerocom PIBA by BASF (hereinafter additive B), and which consists of apolyisobuteneamine as described in example 2 of the patent U.S. Pat. No.7,291,681.

The two additives were each incorporated in a gasoline of RON 98lead-free premium grade gasoline type containing 15% v/v of ETBE (ethyltert-butyl ether), with a degree of treatment of 300 mg of activematerial per kg, in the absence of any other additive.

Evaluation tests on the valve sticking were carried out at +5° C.according to the CEC F16-T-96 method on a VW Waterboxer engine.

The gasoline containing the comparative additive B resulted, in thesetests, in the appearance of valve sticking. With the gasoline containingthe additive A according to the invention, no valve sticking wasobserved.

2.2. Fouling Tests on the Valves at High Temperature (Coking):

The performance qualities of the two additives A and B as regardskeeping the intake valves clean were also evaluated, in accordance withthe standardized method M102E (CEC F-05-93).

These tests were carried out on a reference gasoline, in which one orother of the additives A and B was incorporated, at different degrees oftreatment.

The results obtained are described in detail in the table below:

Amount of deposits Degree of treatment CEC F-05-93 Additive (mg/kg)(mg/valve) None — 321 A 200 1442 A 100 1277 A 50 1072 B 100 877 B 200 30

The two tests above show that the effects of one and the same additiveon the deposits capable of forming on the fuel intake valves in sparkignition engines vary substantially, according to whether deposits whichform at low temperature (valve sticking) or at high temperature (coking)are concerned.

Thus, the additive B, which is conventionally employed to prevent thefouling of the valves by coking during the operation of the engine athigh temperature, results in deposits at low temperature, which bringabout a phenomenon of valve sticking.

On the other hand, the additive A according to the invention makes itpossible to effectively prevent valve sticking but does notautomatically result in good performance qualities for preventing thecoking at high temperature.

1. The use, in order to prevent deposits at low temperature on the fuelintake valves in indirect injection spark ignition engines, of one ormore copolymer(s) comprising:  at least one unit of following formula(I):

in which: u=0 or 1, R₁′ represents a hydrogen atom or a methyl group, Erepresents —O— or —N(Z)— or —O—CO— or —CO—O— or —NH—CO— or —CO—NH—, withZ representing H or a C₁ to C₆ alkyl group, G represents a group chosenfrom a C₁ to C₃₄ alkyl group, an aromatic nucleus, an aralkyl groupcomprising at least one aromatic nucleus and at least one C₁ to C₃₄alkyl group, and  at least one unit of following formula (II):

in which: v=0 or 1, R₁″ is chosen from the hydrogen atom and the methylgroup, Q is chosen from the oxygen atom and an —NR′— group with R′ beingchosen from a hydrogen atom and C₁ to C₁₂ hydrocarbon chains, Rrepresents a C₁ to C₃₄ hydrocarbon chain which can also contain one ormore nitrogen and/or oxygen atoms and/or carbonyl groups, which issubstituted by at least one amino group comprising a primary, secondaryor tertiary amine or quaternary ammonium functional group, andoptionally one or more hydroxyl groups.
 2. The use of a copolymer asrecited in claim 1, in which the amino group present in the group R ofthe formula (II) is chosen from: the groups having at least one amine,imine, amidine, guanidine, aminoguanidine or biguanidine functionalgroup, such as alkylamines, polyalkylenepolyamines, polyalkylenimines,alkylimines, alkylamidines, alkylguanidines and alkylbiguanidines, itbeing possible for the alkyl substituent to be linear or branched,cyclic or acyclic, and preferably having from 1 to 34 carbon atoms, morepreferentially from 1 to 12 carbon atoms, and the quaternized forms ofthese groups; and monocyclic or polycyclic heterocyclic groups, havingfrom 3 to 34 atoms, preferably from 5 to 12 atoms, more preferentiallyfrom 6 to 10 atoms, and at least one nitrogen atom, it being understoodthat the polycyclic heterocyclic groups have, optionally, fused rings.3. The use of a copolymer as recited in claim 1, in which the group R ofthe formula (II) is represented: when v has the value 1, by the formula(V):L-R′₂  (V) when v has the value 0, by the formula (V) or the formula(V′):L-R′₂  (V)L-  (V′) in which formulae (V) and (V′): R₂′ is chosen from C₁ to C₃₄hydrocarbon chains, optionally substituted by at least one hydroxylgroup, and  L is chosen from the group consisting of:  the followinggroups: amine: —NH₂; —NHR_(a), —NR_(a)R_(b); imine: —HC═NH; —HC═NR_(a);—N═CH₂, —N═CR_(a)H; —N═CR_(a)R_(b); amidine: —(C═NH)—NH₂;—(C═NH)—NR_(a)H; —(C═NH)—NR_(a)R_(b); —(C═NR_(a))—NH₂;—(C═NR_(a))—NR_(b)H; —(C═NR_(a))—NR_(b)R_(c); —N═CH(NH₂);—N═CR_(a)(NH₂); —N═CH(NR_(a)H); —N═CR_(a)(NR_(a)H); —N═CH(NR_(a)R_(b));—N═CR_(a)(NR_(b)R_(c)); guanidine: —NH—(C═NH)—NH₂; —NH—(C═NH)—NHR_(a);—N═C(NH₂)₂; —N═C(NR_(a)H)₂; —N═C(NR_(a)R_(b))₂; —N═C(NR_(a)H)(NR_(b)H);aminoguanidine: —NH—(C═NH)—NH—NH₂; —NH—(C═NH)—NH—NHR_(a);—N═C(NH₂)(NH—NH₂); —N═C(NR_(a)H)(NH—NH₂); —N═C(NR_(a)H)(NR′—NH₂);—N═C(NR_(a)R_(b))(NH—NH₂); —N═C(NR_(a)R_(b))(NR_(a)—NH₂); biguanidine:—NH—(C═NH)—NH—(C═NH)—NH₂; —NH—(C═NH)—NH—(C═NH)—NHR_(a);—N═C(NH₂)—NH—(C═NH)—NH₂; —N═C(NH₂)—NH—(C═NR_(a))—NH₂;—N═C(NH₂)—NH—(C═NH)—NR_(a)H; —N═C(NH₂)—NH—(C═NR_(a))—NR_(b)H;—N═C(NH₂)—NH—(C═NH)—NR_(a)R_(b); —N═C(NH₂)—NH—(C═NR_(a))—NR_(b)R_(c);—N═C(NR_(a)H)—NH—(C═NH)—NH₂; —N═C(NR_(a)H)—NH—(C═NR_(b))—NH₂;—N═C(NR_(a)H)—NH—(C═NH)—NR_(b)H; —N═C(NR_(a)H)—NH—(C═NR_(b))—NR_(c)H;—N═C(NR_(a)H)—NH—(C═NH)—NR_(b)R_(c);—N═C(NR_(a)H)—NH—(C═NR_(b))—NR_(c)R_(d);—N═C(NR_(a)R_(b))—NH—(C═NH)—NH₂; —N═C(NR_(a)R_(b))—NH—(C═NR_(c))—NH₂;—N═C(NR_(a)R_(b))—NH—(C═NH)—NR_(c)H;—N═C(NR_(a)R_(b))—NH—(C═NR_(c))—NR_(d)H;—N═C(NR_(a)R_(b))—NH—(C═NH)—NR_(c)R_(d);—N═C(NR_(a)R_(b))—NH—(C═NR_(c))—NR_(d)R_(e); the quaternized forms ofthe above groups, when these contain at least one quaternizable nitrogenatom; and polyamine and polyalkylenepolyamine groups, in particularthose of formulae —NH—(R_(f)—NH)_(k)—H; —NH—(R_(f)—NH)_(k)—R_(a); withR_(a), R_(b), R_(c), R_(d) and R_(e) representing, independently of oneanother, a C₁-C₃₄, preferably C₁-C₁₂, alkyl group, optionally comprisingone or more NH₂ functional groups and one or more —NH— bridges; R_(f)represents a C₁-C₆, preferably C₂-C₄, alkyl group; k represents aninteger ranging from 1 to 20, preferably from 2 to
 12. 4. The use of acopolymer as recited in claim 1, in which the copolymer contains unitsof formula (II) comprising a group R containing at least one quaternaryammonium functional group.
 5. The use of a copolymer as recited in claim4, in which from 5 mol % to 95 mol % of the units of formula (II) of thecopolymer comprise, in the group R, at least one quaternary ammoniumfunctional group, preferably from 10% to 90%, more preferentially from20% to 80% and more preferentially still from 40% to 60%, with respectto the total molar amount of units of formula (II) in the copolymer. 6.The use of a copolymer as recited in claim 1, in which the quaternaryammonium functional group(s) optionally present in the group R of theunits of formula (II) is (are) represented by one of the followingformulae (III) and (IV):

in which: X⁻ is chosen from hydroxide or halide ions and organic anions,preferably organic anions, R₂ is chosen from C₁ to C₃₄ hydrocarbonchains, optionally substituted by at least one hydroxyl group, R₃, R₄and R₅ are identical or different and are chosen independently from C₁to C₁₈ hydrocarbon chains, it being understood that the R₃, R₄ and R₅groups can contain one or more groups chosen from: a nitrogen atom, anoxygen atom and a carbonyl group and that the R₃, R₄ and R₅ groups canbe connected together in pairs to form one or more rings, R₆ and R₇ areidentical or different and are chosen independently from C₁ to C₁₈hydrocarbon chains, it being understood that the R₆ and R₇ groups cancontain one or more groups chosen from: a nitrogen atom, an oxygen atomand a carbonyl group and that the R₆ and R₇ groups can be connectedtogether to form a ring.
 7. The use of a copolymer as recited in claim6, in which the quaternary ammonium functional group(s) present in thegroup R of the units of formula (II) is (are) represented by the formula(III), in which: X⁻ is chosen from organic anions, preferably conjugatebases of carboxylic acids, R₂ is chosen from C₁ to C₃₄ hydrocarbonchains, preferably C₁ to C₁₈ alkyl groups, R₃, R₄ and R₅ are identicalor different and are chosen independently from C₁ to C₁₈ hydrocarbonchains, optionally substituted by at least one hydroxyl group, it beingunderstood that at least one of the R₃, R₄ and R₅ groups contains one ormore hydroxyl group(s).
 8. The use of a copolymer as recited in claim 1,in which, in the formula (I), the group G is a C₄ to C₃₄ alkyl.
 9. Theuse of a copolymer as recited in claim 1, in which, in the formula (I),R₁′ is a hydrogen atom.
 10. The use of a copolymer as recited in claim1, in which, in the formula (I), the group E is chosen from: —O— and—N(Z)—, with Z representing H or a C₁ to C₆ alkyl group.
 11. The use ofa copolymer as recited in claim 1, in which, in the formula (I), thegroup E is chosen from: —O—CO— and —NH—CO—; preferably, the group E isthe —O—CO— group, it being understood that the group E=—O—CO— isconnected to the vinyl carbon by the oxygen atom and that the groupE=—NH—CO— is connected to the vinyl carbon by the nitrogen atom.
 12. Theuse of a copolymer as recited in claim 1, in which, in the formula (I),the group E is chosen from: —CO—O— and —CO—NH—; preferably the group Eis the —CO—O— group, it being understood that the group E is connectedto the vinyl carbon by the carbon atom.
 13. The use of a copolymer asrecited in claim 1, in which the copolymer is chosen from blockcopolymers and random copolymers; preferably, the copolymer is a blockcopolymer.
 14. The use of a copolymer as recited in claim 13, in whichthe copolymer is a block copolymer comprising at least:  a block Acorresponding to the following formula (XI):

in which: p is an integer ranging from 2 to 100, preferably ranging from5 to 80, preferably ranging from 10 to 70, more preferentially rangingfrom 20 to 60, and R₁′, u, E and G are as defined in claim 1, and  ablock B corresponding to the following formula (XII):

in which: n is an integer ranging from 2 to 50, preferably from 3 to 40,more preferentially from 4 to 20, more preferentially still from 5 to10, R₁″, v, Q and R are as defined in claim
 1. 15. The use of acopolymer as recited in claim 14, in which, from 5 mol % to 95 mol % ofthe units of the block B comprise a group R containing at least onequaternary ammonium functional group.
 16. The use of a copolymer asrecited in claim 15, in which the block B comprises from 5 mol % to 95mol % of units corresponding to the formula (XIII):

in which: R₁″ is chosen from the hydrogen atom and the methyl group, Qis chosen from the oxygen atom and the —NR′— group, with R′ being chosenfrom a hydrogen atom and C₁ to C₁₂ hydrocarbon chains, X⁻ is chosen fromorganic anions, preferably conjugate bases of carboxylic acids, R₂ ischosen from C₁ to C₃₄ hydrocarbon chains, preferably C₁ to C₁₈ alkylgroups, R₃, R₄ and R₅ are identical or different and are chosenindependently from C₁ to C₁₈ hydrocarbon chains, optionally substitutedby at least one hydroxyl group, it being understood that at least one ofthe R₃, R₄ and R₅ groups contains at least one hydroxyl group.
 17. Theuse of a copolymer as recited in claim 15, in which: the block Aconsists of a chain of structural units derived from a C₁-C₃₄ alkyl(meth)acrylate monomer, and the block B consists of a chain ofstructural units derived from alkyl (meth)acrylate oralkyl(meth)acrylamide monomers, 5 mol % to 95 mol % of which have analkyl radical consisting of a C₁ to C₃₄ hydrocarbon chain substituted bya quaternary ammonium group and optionally one or more hydroxyl groups,and 5 mol % to 95 mol % of which have an alkyl radical consisting of aC₁ to C₃₄ hydrocarbon chain substituted by a group chosen from primary,secondary or tertiary amines, preferably tertiary amines, and optionallyone or more hydroxyl groups.
 18. The use of a copolymer as recited inclaim 1, in which the copolymer is incorporated in a liquid fuel in atotal content of at least 5 ppm by weight, preferably of at least 10ppm, more preferentially at a content of 10 to 5000 ppm, morepreferentially still of 20 to 2000 ppm and better still of 50 to 1000ppm.
 19. The use of a copolymer as recited in claim 1, for preventingthe sticking of said valves, which is determined according to thestandardized method CEC F-16-T96.
 20. A process for keeping clean, atlow temperature, the fuel intake valves in an indirect injection sparkignition engine comprising at least the following stages: thepreparation of a fuel composition by additivation of a fuel with acopolymer as defined in claim 1, then the injection of said fuelcomposition into the spark ignition engine.